What is the initial product of transcription called?

The initial product is called pre-mRNA, a precursor to mature mRNA.

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What modifications are made to pre-mRNA after transcription but before translation?

  1. Addition of a 5' cap - this helps stabilise mRNA and delay degradation, and also helps mRNA bind to ribosomes
  2. Addition of a 3' poly-A tail - helps stabilise mRNA and delay degradation
  3. Splicing - the removal of introns and joining of exons in pre-mRNA

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What are introns and exons?

  1. Introns - non-coding regions of DNA.
  2. Exons - regions of DNA that code for polypeptides.

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How does RNA editing alter mRNA?

RNA editing changes the nucleotide sequence through base addition, deletion or substitution in a similar manner to how point mutations work.


This allows many different proteins to be synthesised from one mRNA molecule.

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What is the effect of mRNA stability and degradation on protein synthesis?

More stable mRNA lasts longer, leading to increased translation and so protein synthesis.


If mRNA is less stable, it degrades more quickly, cannot be translated and protein synthesis decreases.

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How do inhibitory proteins affect mRNA?

Inhibitory proteins bind to mRNA to prevent its attachment to ribosomes during translation.


This decreases protein synthesis.

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What role do initiation factors have in translation?

Initiation factors, when activated, help mRNA bind to ribosomes, initiating translation and so increasing protein synthesis.

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What is the role of protein kinases in protein modification?

Protein kinases are enzymes that add phosphate groups to proteins, phosphorylating them. This changes a protein's tertiary structure and so changes their function.


 Many enzymes are activated via phosphorylation.


Protein kinases themselves are often activated by the second messenger cyclic AMP (cAMP).

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What is post-translational control, and what modifications might it involve?

Post-translational control involves modifications to proteins after synthesis, affecting their function.

Examples of these modifications include:

  1. Addition of non-protein groups like carbohydrates, lipids, or phosphates
  2. Amino acid modification and formation of disulfide bridges between amino acids
  3. Folding, or shortening of proteins
  4. Modification by cAMP


An example of post-translational control by cAMP is shown in the lac operon.

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What is the difference between introns and exons?

Introns are non-coding regions that do not code for amino acids, whereas exons are coding regions that do code for amino acids.

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What is splicing?

Splicing is the process of removing introns from a pre-mRNA molecule.

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Why does prokaryotic mRNA not undergo splicing?

Prokaryotic DNA does not contain introns.

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